Index: /trunk/src/VBox/Frontends/VirtualBox/src/settings/machine/UIMachineSettingsNetwork.cpp
===================================================================
--- /trunk/src/VBox/Frontends/VirtualBox/src/settings/machine/UIMachineSettingsNetwork.cpp	(revision 42252)
+++ /trunk/src/VBox/Frontends/VirtualBox/src/settings/machine/UIMachineSettingsNetwork.cpp	(revision 42253)
@@ -56,5 +56,5 @@
     /* Setup widgets: */
     m_pAdapterNameCombo->setInsertPolicy(QComboBox::NoInsert);
-    m_pMACEditor->setValidator(new QRegExpValidator(QRegExp("[0-9A-Fa-f][02468ACEace][0-9A-Fa-f]{10}"), this));
+    m_pMACEditor->setValidator(new QRegExpValidator(QRegExp("[0-9A-Fa-f]{12}"), this));
     m_pMACEditor->setMinimumWidthByText(QString().fill('0', 12));
 
@@ -164,4 +164,5 @@
 {
     m_pValidator = pValidator;
+    connect(m_pMACEditor, SIGNAL(textEdited(const QString &)), m_pValidator, SLOT(revalidate()));
 }
 
@@ -215,4 +216,21 @@
             break;
     }
+
+    /* Validate MAC-address: */
+    if (m_pMACEditor->text().size() < 12)
+    {
+        strWarning = tr("the value of the Mac address field in not complete.");
+        fValid = false;
+    }
+    else
+    {
+        QRegExp validator("[0-9A-Fa-f][02468ACEace][0-9A-Fa-f]{10}");
+        if (!validator.exactMatch(m_pMACEditor->text()))
+        {
+            strWarning = tr("the second digit cannot be odd, as only unicast Mac addresses allowed.");
+            fValid = false;
+        }
+    }
+
     if (!fValid)
         strTitle += ": " + vboxGlobal().removeAccelMark(tabTitle());